STEM. LATICIFEROUS TISSUES. 89 



will be found that they originate from a number of originally 

 separate cells of the cambium, the cavities of which are thrown 

 together by the partial or complete absorption of the walls. 

 Such fusions may appear in the terminal or the lateral walls. 



ii. Laticiferovs Cells, 



I. Cut tangential sections of the cortex of Euphorbia 

 splendens (other species will do) just outside the vascular 

 ring, and mount in water, or dilute glycerine. 



Examine with a low power. 



Running through the cortical parenchyma will be 

 seen long tubes, with thick cellulose walls and granular 

 contents. These are the laticiferous cells, which 

 differ from the preceding in being developed, not by 

 fusion of originally distinct cells, but by continued 

 apical growth of single cells. 



Note cases of branching of these cells. 



Included in the granular contents are starch-grains 

 of peculiar dumb-bell form. 



Treat sections with iodine solution, and observe the 

 effect on these bodies. 



II. Cut transverse sections of the same stem, and note 

 the distribution of the laticiferous cells ; they may be 

 recognised by their walls, which are thicker than those 

 of the surrounding tissues, and appear circular in 

 section. 



III. Separate the whole cortex from a piece of the 

 stem ; boil it in potash for about five minutes, and tease 

 out the long laticiferous cells with needles ; mount, and 

 observe with a low power. They appear as long cylin- 

 drical structures, with thick walls (note striation). 

 Observe occasional branching. They are usually 

 broken at the ends. 



